As show in FIGS. 1 and 2, a collapsible support frame of the prior art comprises a cylindrical main body and four support legs. The cylindrical main body is formed of an inner tube 1 and an outer tube 1' into which the inner tube 1 is fitted. The inner tube 1 is provided in the tube wall with a threaded hole 11, and in the outer wall of the top end thereof with a protruded portion 12. The outer tube 1' is provided in the tube wall with a through hole 13 is corresponding in location to the threaded hole 11 of the inner tube 1. The notch 14 is corresponding location and size to the protruded portion 12 of the inner tube 1. The inner tube 1 is fitted into the outer tube 1' such that the protruded portion 12 of the inner tube 1 is stopped by the notch 14 of the outer tube 1' and that the inner tube 1 is held in the outer tube 1' securely by a fastening bolt 15 which is engaged with the threaded hole 11 of the inner tube 1 via the through hole 13 of the outer tube 1'. In assembling the inner tube 1 and the outer tube 1', the threaded hole 11 and the through hole 13 must be aligned. In disassembling the inner tube 1 and the outer tube 1', the fastening bolt 15 must be first unfastened. In addition, the protruded portion 12 and the notch 14 undermine the esthetic effect of the collapsible support frame of the prior art.